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Category: Integration

Question-91290

Question Number 91290 by mhmd last updated on 29/Apr/20 Commented by MJS last updated on 29/Apr/20 $$\mathrm{let}\:{n}=\mathrm{2}{k} \\ $$$$\underset{\mathrm{2}{k}} {\overset{\mathrm{2}\left({k}+\mathrm{1}\right)} {\int}}\frac{{dx}}{\left(\mathrm{1}+\mathrm{3}^{\mathrm{cos}\:{x}} \right)\left(\mathrm{1}+\mathrm{3}^{\mathrm{sin}\:{x}} \right)}\approx\mathrm{1}.\mathrm{57079632679}=\frac{\pi}{\mathrm{2}} \\ $$$$\Rightarrow\:\mathrm{answer}\:\mathrm{is}\:\frac{\pi{n}}{\mathrm{2}}…

f-is-a-function-that-assigns-to-each-natural-number-multiplication-of-its-digits-for-exampl-f-200-0-f-128-1-2-8-16-find-the-value-of-f-100-f-101-f-

Question Number 156775 by mnjuly1970 last updated on 15/Oct/21 $$ \\ $$$$\:\:\:{f}\:\:{is}\:\:{a}\:{function}\:{that}\:{assigns} \\ $$$$\:\:\:{to}\:{each}\:{natural}\:{number}\: \\ $$$$\:\:\:\:\:{multiplication}\:{of}\:{its}\:{digits}\: \\ $$$$\:\:\:\:{for}\:{exampl}\::\:\:{f}\left(\:\mathrm{200}\right)=\mathrm{0} \\ $$$$\:\:\:\:{f}\:\left(\:\mathrm{128}\:\right)=\mathrm{1}×\mathrm{2}×\mathrm{8}\:=\mathrm{16} \\ $$$$\:\:\:\:\:{find}\:{the}\:{value}\:{of}\:: \\ $$$$\:\:\:\:\:{f}\:\left(\mathrm{100}\right)\:+\:{f}\left(\mathrm{101}\:\right)+\:{f}\:\left(\mathrm{102}\:\right)+…{f}\left(\mathrm{999}\right)=? \\…

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Question Number 156761 by gsk2684 last updated on 15/Oct/21 $${prove}\:{that} \\ $$$$\int\frac{{a}\:+\:{b}\:\mathrm{sin}\:{x}}{\left({b}\:+\:{a}\:\mathrm{sin}\:{x}\right)^{\mathrm{2}} }{dx}=\frac{−\mathrm{cos}\:{x}}{{b}\:+\:{a}\:\mathrm{sin}\:{x}} \\ $$ Answered by cortano last updated on 15/Oct/21 $$\:\frac{\mathrm{d}}{\mathrm{dx}}\int\frac{\mathrm{a}+\mathrm{bsin}\:\mathrm{x}}{\left(\mathrm{b}+\mathrm{asin}\:\mathrm{x}\right)^{\mathrm{2}} }\:\mathrm{dx}=\frac{\mathrm{d}}{\mathrm{dx}}\left(\frac{−\mathrm{cos}\:\mathrm{x}}{\mathrm{b}+\mathrm{asin}\:\mathrm{x}}\right) \\…

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Question Number 25682 by abdo imad last updated on 13/Dec/17 $${we}\:{give}\:\int_{\mathrm{0}} ^{\infty} \:{t}^{{a}−\mathrm{1}} \left(\mathrm{1}\:+\:{t}\right)^{−\mathrm{1}} {dt}\:=\pi\:\left({sin}\left(\pi{a}\right)\right)^{−\mathrm{1}} \:{with}\:\mathrm{0}<{a}<\mathrm{1}\:{find}\:{the}\:{value}\:{of}\:\int_{\mathrm{0}} ^{\infty} \:\left(\mathrm{1}\:+{x}^{\mathrm{16}} \right)^{−\mathrm{1}} {dx} \\ $$ Answered by ajfour…